1. Field of the Invention
The present invention relates to a display device. More particularly, the present invention relates to an adhesive material cured in a relatively low temperature and used as an electric connection, a display device using the adhesive material and a method of fabricating the display device.
2. Discussion of the Related Art
Recently, as society has entered in earnest upon an information age, a field of display devices that represent all sorts of electrical signals as visual images has developed rapidly. Flat panel display device, such as a liquid crystal display (LCD) device and an organic light emitting diode (OLED) device, having characteristic in thin profile, lightweight and low power consumption has been introduced.
Since the LCD device including a thin film transistor (TFT) as a switching element, referred to as an active matrix LCD (AM-LCD) device, has excellent characteristics of high resolution and displaying moving images, the AM-LCD device has been widely used.
On the other hand, since the OLED device has excellent characteristics of high brightness, a low power consumption and high contrast ratio, the OLED device has been widely used. Moreover, the OLED device has advantages such as a high response rate, and a low production cost.
Both the LCD device and the OLED device require an array substrate including a thin film transistor (TFT) as a switching element for control ON and OFF of each pixel region. In a non-display region of the array substrate, a printed circuit board (PCB) including a plurality of drive integrated circuit (IC) for driving elements of the array substrate is installed through a tape carrier package (TCP).
In more detail, in the non-display regions at an upper side and a left side of the array substrate, a gate pad electrode and a data pad electrode for electrical connection with an exterior circuit are respectively formed. In addition, a gate link line and a data link line respectively connecting to the gate pad electrode and the data pad electrode are formed.
In a display region of the array substrate, a gate line, which is connected to the gate pad electrode through the gate link line and extends along a horizontal direction, and a data line, which is connected to the data pad electrode through the data link line and extends along a vertical direction, are formed. The gate and data lines cross each other to define the pixel region. The TFT is formed at a crossing portion of the gate and data lines.
In the LCD device, a pixel electrode, which is connected to a drain electrode of the TFT, is formed in the pixel region. In addition, the LCD device includes a color filter substrate, where a color filter layer and a common electrode are formed, facing the array substrate. A liquid crystal layer is formed between the array substrate and the color filter substrate to form a liquid crystal panel of the LCD device.
On the other hand, in the OLED device, an organic emitting diode including an organic emitting layer is formed on the array substrate, and a counter substrate for encapsulation is disposed on the organic emitting diode.
As mentioned above, the PCB including the drive IC for driving the array substrate is installed on the array substrate. For example, the PCB is installed on the array substrate by a tape automated bonding process. As a result, the drive IC of the PCB is electrically connected to the gate pad electrode and the data pad electrode.
FIGS. 1A to 1C are cross-sectional views showing a conventional bonding process of the drive IC to the liquid crystal panel.
As shown in FIG. 1A, in the display device 10 including first and second substrates 5 and 7, an anistropic conductive film (ACF) 20 is disposed on a pad electrode (not shown) at the non-display region of the first substrate 5. The anistropic conductive film 20 includes conductive balls therein. The first substrate 5 may be the array substrate, and the pad electrode is the gate pad electrode or the data pad electrode. Next, the drive IC (30) is disposed over the anistropic conductive film 20.
Next, as shown in FIG. 1B, a thermal pressing unit 50 such as a heating bar is disposed on the drive IC 30 with a buffer film therebetween. The drive IC 30 is thermally pressed such that the pad electrode (not shown) and electrodes (not shown) in the drive IC 30 are electrically connected and adhered to each other by the anistropic conductive film 20 as shown in FIG. 1C.
However, in the thermal pressing process, there is a difference in a thermal expansion between the array substrate 5 and the drive IC 30. As a result, when the array substrate 5 and the drive IC 30 are cooled into a room temperature, there are warpage defects on the drive IC 30. These defects may be referred to as a smile defects.
In addition, there is a peeling process of the anisotropic conductive film such that the electrical connection between the drive IC and the pad electrode is destroyed.
On the other hand, requirement for the narrow bezel type display device, where the non-display region has a width of 0.5 to 2.0 mm, is increased. In the narrow bezel type display device, a polarization plate is formed on the color filter substrate may cover the pad electrode in the non-display region to increase ambient contrast ratio. In this instance, when the drive IC is installed on the array substrate by the above thermal pressing process, which is processed under a relatively high temperature of 150 to 190° C., the polarization plate may be damaged by heat in the thermal pressing process.
On the other hand, in a full HD display device, a distance between adjacent pad electrodes becomes narrowed. In this instance, when the drive IC and the pad electrode are connected using the anistropic conductive film 20, an electrical short problem between adjacent pad electrodes is generated.